Display device and method for fabricating the same

ABSTRACT

An inexpensive display device, as well as an electrical apparatus employing the same, can be provided. In the display device in which a pixel section and a driver circuit are included on one and the same insulating surface, the driver circuit includes a decoder  100  and a buffer section  101 . The decoder  100  includes a plurality of NAND circuits each including p-channel TFTs  104  to  106  connected to each other in parallel and other p-channel TFTs  107  to  109  connected to each other in series. The buffer section  101  includes a plurality of buffers each including three p-channel TFTs  114  to  116.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a device having an element inwhich a light-emitting material is interposed between electrodes(hereinafter, such a device is referred to as the light-emitting deviceand such an element is referred to as the light-emitting element). Inparticular, the present invention relates to a device including on oneand the same insulating surface, a pixel section and a driver circuitfor transmitting a signal to the pixel section. In addition, the presentinvention can be used for a device having an element in which liquidcrystal is interposed between electrodes (hereinafter, such a device isreferred to as the liquid crystal display device and such an element isreferred to as the liquid crystal element). It should be noted that inthe present specification, the light-emitting device and the liquidcrystal display device are collectively referred to as the displaydevice.

[0003] Light-emitting materials that can be used in the presentinvention include all of light-emitting materials that emit light(phosphorescent light and/or fluorescent light) via singlet excitationor triplet excitation, or both of these excitations.

[0004] 2. Description of the Related Art

[0005] Recently, developments for a light-emitting device including alight-emitting element which utilizes a light-emitting material capableof providing EL (Electro Luminescence) has been progressed (hereinafter,such a light-emitting device is simply referred to as the light-emittingdevice; such a light-emitting element is referred to as the EL element;and such a light-emitting material is referred to as the EL material).The light-emitting device has a structure having an EL element in whicha thin film made of the EL material is interposed between an anode and acathode.

[0006] Although in the developments for the light-emitting devices thepassive-matrix type devices have been mainly focused, it has beenconsidered that there will exist disadvantages with the passive-matrixtype light-emitting devices in that a sufficient reliability (a longlifetime of the EL element) cannot be ensured with a higher precisionpixel section which requires the luminance of the EL element to beincreased. From the above circumstances, the active-matrix typelight-emitting devices are recently drawing much attention for thepurpose of realizing a higher precision display. The active-matrix typelight-emitting device is characterized in that an active element isprovided within each pixel so that the EL element is allowed to emitlight in accordance with an input signal. As the active element, a TFT(Thin Film Transistor) is commonly employed.

[0007] Reference is now made to FIG. 4, which illustrates a pixelstructure of the active-matrix type light-emitting device. In FIG. 4,reference numeral 401 denotes a source wiring, 402 denotes a gatewiring, 403 denotes a TFT functioning as a switching element(hereinafter referred to as the switching TFT), and 404 denotes acapacitor electrically connected to a drain of the switching TFT 403.

[0008] The drain of the switching TFT 403 is also electrically connectedto a gate electrode of a current-controlling TFT 405. A source of thecurrent-controlling TFT 405 is electrically connected to a currentsupply line 406, while a drain thereof is electrically connected to anEL element 407. In other word, the current-controlling TFT 405 canfunction as an element for controlling current flowing through the ELelement 407.

[0009] The luminance of the EL element can be controlled by thusproviding the two TFTs having different functions, respectively, in eachof the pixels. As a result, a light-emitting period can substantiallycorrespond to one-frame period, and an image can be displayed whilesuppressing the luminance even with a higher precision pixel section.Furthermore, advantages of the active-matrix type device include thecapability of forming, as a driver circuit for transmitting a signal tothe pixel section, a shift register or a sampling circuit with TFTs onthe same substrate. This enables fabrication of a very compactlight-emitting device.

[0010] However, it is difficult to ensure a sufficient production yieldof the active-matrix type light-emitting device, as compared to thepassive-matrix type device that has a simpler structure, since aplurality of TFTs have to be formed on the same substrate in theactive-matrix type device. Particularly in the case where the drivercircuit is to be provided on the same substrate, a line defect may arisein which one line of the pixels does not operate because of a defect ofoperation. In addition, since fabrication steps for the TFTs arerelatively complicated, there is the higher possibility of increasing afabrication cost of the active-matrix type device, as compared to thatof the passive-matrix type device. In such a case, a disadvantage ofincreasing a price of an electrical apparatus employing theactive-matrix type light-emitting device in its display section mayarise.

[0011] Thus, the present invention is intended to reduce a fabricationcost of the active-matrix type display device so as to provide aninexpensive display device. In addition, the present invention is alsointended to provide an inexpensive electrical apparatus that employs inits display section, the display device in accordance with the presentinvention.

SUMMARY OF THE INVENTION

[0012] In accordance with the present invention, in order to reduce afabrication cost of an active-matrix type display device, all of theTFTs to be used in a pixel section are provided as a TFT of oneconductivity type (indicating herein either a p-channel TFT or ann-channel TFT), and furthermore, a driver circuit is also formedentirely with TFTs of the same conductivity type as in the pixelsection. Thus, a fabrication process can be significantly reduced, andtherefore, the fabrication cost can be reduced.

[0013] For the above purpose, in accordance with one aspect of thepresent invention, all of a source wiring, a gate electrode, a gatewiring (which is a line that transmits a signal to the gate electrode),and a current supply line are simultaneously formed. In other word, anidentical electrically conductive (hereinafter simply referred to as“conductive”) film is formed on the same surface. In addition, inaccordance with another aspect of the present invention, a line(referred to as the connecting wiring in the present specification) thatconnects the TFT to a line for connecting a plurality of independentlyformed gate wirings to each other, or the source wiring, or the currentsupply line, is formed on the same surface with the identical conductivefilm as the drain wiring of the current-controlling TFT.

[0014] Furthermore, in accordance with a further important aspect of thepresent invention, a driver circuit is formed of TFTs of one and thesame conductivity type. In other word, in contrast to the conventionaldriver circuit that is in general designed based on a CMOS circuit inwhich an n-channel TFT and a p-channel TFT are complimentarily combinedto each other, the driver circuit in accordance with the presentinvention is formed by combining only the p-channel TFTs or then-channel TFTs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the accompanying drawings:

[0016]FIG. 1 shows a structure of a gate-side driver circuit;

[0017]FIG. 2 shows a timing chart of decoder input signals;

[0018]FIG. 3 shows a structure of a source-side driver circuit;

[0019]FIG. 4 shows a circuit structure of a pixel section of alight-emitting device;

[0020]FIG. 5 shows a cross-sectional structure of the pixel section ofthe light-emitting device;

[0021]FIG. 6 shows a top-view structure of the pixel section of thelight-emitting device;

[0022] FIGS. 7(A) and 7(B) each show another cross-sectional structureof the pixel section of the light-emitting device;

[0023] FIGS. 8(A) through 8(D) show various fabrication steps of thelight-emitting device;

[0024] FIGS. 9(A) through 9(C) show various fabrication steps of thelight-emitting device;

[0025]FIG. 10 shows another circuit structure of a pixel section of alight-emitting device;

[0026]FIG. 11 shows yet another circuit structure of a pixel section ofa light-emitting device;

[0027] FIGS. 12(A) through 12(C) show various fabrication steps of thelight-emitting device;

[0028]FIG. 13 shows another top-view structure of the pixel section ofthe light-emitting device;

[0029] FIGS. 14(A) through 14(C) show various fabrication steps of thelight-emitting device;

[0030]FIG. 15(A) shows yet another top-view structure of the pixelsection of the light-emitting device;

[0031]FIG. 15(B) shows yet another cross-sectional structure of thepixel section of the light-emitting device;

[0032] FIGS. 16(A) and 16(B) show yet other circuit structures of apixel section of a light-emitting device;

[0033] FIGS. 17(A) and 17(B) show yet other circuit structures of apixel section of a light-emitting device;

[0034]FIG. 18 shows a thin film forming apparatus for forming an ELlayer;

[0035] FIGS. 19(A) and 19(B) show external appearances of a liquidcrystal display device;

[0036] FIGS. 20(A) through 20(F) show specific examples of an electricalapparatus, respectively; and

[0037] FIGS. 21(A) through 21(D) show specific examples of an electricalapparatus, respectively;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] With now reference to FIGS. 1 and 2, a driver circuit to be usedin the present invention will be described. In accordance with thepresent invention, instead of a typical shift register, a decoderemploying p-channel TFTs as shown in FIG. 1 is used. FIG. 1 illustratesan example of a gate-side driver circuit.

[0039] In FIG. 1, reference numeral 100 denotes a decoder in thegate-side driver circuit, and 101 denotes a buffer section of thegate-side driver circuit. Here, the buffer section refers to a sectionin which a plurality of buffers (buffer amplifiers) are integrated.Furthermore, the buffer refers to a circuit capable of exhibiting thedriving capability without providing any adverse effects of a subsequentstage on a previous stage.

[0040] The gate-side decoder 100 will be now described. Referencenumeral 102 denotes input signal lines (hereinafter referred to as theselection lines) of the decoder 100, and more specifically indicates A1,A1 bar (a signal having an inverted polarity with respect to A1), A2, A2bar (a signal having an inverted polarity with respect to A2), . . . ,An, and An bar (a signal having an inverted polarity with respect toAn). In other word, it can be considered that the 2n selection lines arearranged.

[0041] The number of the selection lines is determined based on thenumber of gate wirings to be output from the gate-side driver circuit.For example, in the case where a pixel section for VGA display isprovided, 480 gate wirings are required, which in turn requires a totalof 18 selection lines to be provided for 9 bits (corresponding to thecase where n=9). The selection lines 102 transmit signals shown in thetiming chart in FIG. 2. As shown in FIG. 2, assuming that a frequency ofA1 is normalized to be 1, a frequency of A2 can be expressed as 2⁻¹, afrequency of A3 can be expressed as 2⁻², and a frequency of An can beexpressed as 2^(−(n−1)).

[0042] Reference numeral 103 a denotes a first-stage NAND circuit (alsoreferred to as the NAND cell), while 103 b and 103 c denote asecond-stage and an n-th stage NAND circuits, respectively. The requirednumber of the NAND circuits is equal to the number of the gate wirings,and specifically, n NAND circuits are required here. In other word, thedecoder 100 in accordance with the present invention is composed of aplurality of the NAND circuits.

[0043] In each of the NAND circuits 103 a to 103 c, p-channel TFTs 104to 109 are combined to form a NAND circuit. Actually, 2n TFTs areemployed in each of the NAND circuits 103. Furthermore, a gate of eachof the p-channel TFTs 104 to 109 is connected to either one of theselection lines 102 (A1, A1 bar, A2, A2 bar, . . . , An, An bar).

[0044] In this case, in the NAND circuit 103 a, the p-channel TFTs 104to 106 that respectively have the gates connected to any of A1, A2, . .. , An (which are referred to as the positive selection lines) areconnected to each other in parallel, and further connected to a positivepower source wiring (V_(DH)) 110 as a common source, as well as to anoutput line 111 as a common drain. On the other hand, the remainingp-channel TFTs 107 to 109 that respectively have the gates connected toany of A1 bar, A2 bar, . . . , An bar (which are referred to as thenegative selection lines) are connected to each other in series, and asource of the p-channel TFT 109 positioned at one end of the circuit isconnected to a negative power source wiring (V_(DL)) 112 while a drainof the p-channel TFT 107 positioned at the other end of the circuit isconnected to the output line 111.

[0045] As described in the above, the NAND circuit in accordance withthe present invention includes the n TFTs of one conductivity type (thep-channel TFTs in this case) connected in series and the other n TFTs ofthe one conductivity type (the p-channel TFTs in this case) connected inparallel. It should be noted that in the n NAND circuits 103 a to 103 c,all of combinations among the p-channel TFTs and the selection lines aredifferent from each other. In other word, the output lines 111 areconfigured so that only one of them is selected, and signals are inputto the selection lines such that the output lines 111 are sequentiallyselected from one side thereof.

[0046] Then, the buffer 101 is composed of a plurality of buffers 113 ato 113 c so as to respectively correspond to the NAND circuits 103 a to103 c. It should be noted that the buffers 113 a to 113 c may have thesame structure.

[0047] Furthermore, the buffers 113 a to 113 c are formed with p-channelTFTs 114 to 116 as TFTs of one conductivity type. The output line 111from the decoder is input as a gate of the corresponding p-channel TFT114 (a first TFT of the one conductivity type). The p-channel TFT 114utilizes a ground power source wiring (GND) 117 as its source, and agate wiring 118 as its drain. Moreover, the p-channel TFT 115 (a secondTFT of the one conductivity type) utilizes the ground power source line117 as its gate, a positive power source line (V_(DH)) 119 as itssource, and the gate wiring 118 as its drain. The p-channel TFT 115 isalways in the ON state.

[0048] In other words, each of the buffers 113 a to 113 c in accordancewith the present invention includes the first TFT of the oneconductivity type (the p-channel TFT 114), and further includes thesecond TFT of the one conductivity type (the p-channel TFT 115) that isconnected to the first TFT of the one conductivity type in series andutilizes the gate of the first TFT of the one conductivity type as thedrain.

[0049] Furthermore, the p-channel TFT 116 (a third TFT of the oneconductivity type) employs a reset signal line (Reset) as its gate, thepositive power source line 119 as its source, and the gate wiring 118 asits drain. It should be noted that the ground power source line 117 maybe replaced with a negative power source line (which is a power sourceline for providing a voltage that causes a p-channel TFT, to be used asa switching element of a pixel, to be in the ON state).

[0050] In this case, a channel width (indicated as W1) of the p-channelTFT 115 and a channel width (indicated as W2) of the p-channel TFT 114satisfy the relationship of W1<W2. The channel width refers to a lengthof a channel formation region measured in the direction perpendicular toa channel length.

[0051] The buffer 113 a operates as follows. During a time period inwhich a positive voltage is being applied to the output line 111, thep-channel TFT 114 is in the OFF state (i.e., its channel is not formed).On the other hand, since the p-channel TFT 115 is always in the ON state(i.e., its channel is formed), a voltage of the positive power sourceline 119 is applied to the gate wiring 118.

[0052] On the other hand, in the case where a negative voltage isapplied to the output line 111, the p-channel TFT 114 comes into the ONstate. In this case, since the channel width of the p-channel TFT 114 iswider than that of the p-channel TFT 115, the electrical potential ofthe gate wiring 118 is pulled by an output on the side of the p-channelTFT 114, thereby resulting in the electrical potential of the groundpower source line 117 being applied to the gate wiring 118.

[0053] Accordingly, the gate wiring 118 outputs a negative voltage (thatcauses the p-channel TFT, to be used as the switching element of thepixel, to be in the ON state) when a negative voltage is being appliedonto the output line 111, while always outputting a positive voltage(that causes the p-channel TFT, to be used as the switching element ofthe pixel, to be in the OFF state) when a positive voltage is beingapplied onto the output line 111.

[0054] The p-channel TFT 116 is used as a reset switch for forcing thegate wiring 118, to which the negative voltage is being applied, to bepulled up to a positive voltage. Namely, after a selection period of thegate wiring 118 is completed, a reset signal is input so that a positivevoltage is applied to the gate wiring 118. It should be noted that thep-channel TFT 116 may be omitted.

[0055] With the gate-side driver circuit that operates in theabove-described manner, the gate wirings are sequentially selected.Then, the structure of a source-side driver circuit is shown in FIG. 3.The source-side driver circuit as shown in FIG. 3 includes a decoder301, a latch 302, and a buffer 303. Since the decoder 301 and the buffer303 have the identical structures with those of the gate-side drivercircuit, respectively, descriptions therefor are omitted here.

[0056] In the case of the source-side driver circuit shown in FIG. 3,the latch 302 is composed of a first-stage latch 304 and a second-stagelatch 305. Each of the first-stage latch 304 and the second-stage latch305 includes a plurality of basic units 307 each composed of m p-channelTFTs 306 a to 306 c. An output line 308 from the decoder 301 is input togates of the respective m p-channel TFTs 306 a to 306 c that form thebasic unit 307. It should be noted that the number m is any integer.

[0057] For example, in the case of the VGA display, the number of thesource wirings is 640. In the case where m=1, the number of the NANDcircuits required to be provided is also 640, while 20 selection lines(corresponding to 10 bits) are required to be provided. On the otherhand, however, when m=8, the number of the necessary NAND circuits is 80and the number of the necessary selection lines is 14 (corresponding to7 bits). Namely, assuming that the number of the source wirings is M,the number of necessary NAND circuits can be expressed as M/m.

[0058] Sources of the p-channel TFTs 306 a to 306 c are connected tovideo signal lines (V1, V2, . . . , Vk) 309, respectively. Namely, whena negative voltage is applied to an output line 308, all of thep-channel TFTs 306 a to 306 c are simultaneously put into the ON state,so that video signals are taken into the corresponding p-channel TFTs306 a to 306 c, respectively. The video signals thus taken in areretained in capacitors 310 a to 310 c, respectively, connected thereto.

[0059] Furthermore, the second-stage latch 305 also includes a pluralityof basic units 307 b each composed of m p-channel TFTs 311 a to 311 c.All of gates of the p-channel TFTs 311 a to 311 c are connected to alatch signal line 312, so that when a negative voltage is applied to thelatch signal line 312, all of the p-channel TFTs 311 a to 311 c aresimultaneously turned on.

[0060] As a result, the signals retained in the capacitors 310 a to 310c are then retained respectively in capacitors 313 a to 313 c connectedto the p-channel TFTs 311 a to 311 c, and simultaneously output to thebuffer 303. Then, as described with reference to FIG. 1, those signalsare output to the source wirings 314 via the buffer. With thesource-side driver circuit that operates in the above-described manner,the source wirings are sequentially selected.

[0061] As described in the above, by composing the gate-side drivercircuit and the source-side driver circuit only of the p-channel TFTs,all of the pixel sections and the driver circuits can be entirely formedof the p-channel TFTs. Accordingly, upon fabrication of an active-matrixtype display device, a fabrication yield and a throughput of the TFTsteps can be significantly improved, thereby resulting in a reducedfabrication cost.

[0062] It should be noted that the present invention can be embodiedeven in the case where either of the source-side driver circuit or thegate-side driver circuit, or both of them, are provided in an IC chip tobe externally attached.

Embodiment 1

[0063] In the present invention, the pixel section, in addition to thedriver circuit, is entirely composed of the p-channel TFTs. Thus, in thepresent embodiment, the structure of the pixel section for displaying animage in accordance with the signals transmitted by the driver circuitas shown in FIGS. 1 and 3 will be described.

[0064] The structure of a pixel of an active-matrix type light-emittingdevice in accordance with the present invention is shown in FIGS. 5 and6. FIG. 5 illustrates a cross-sectional view of one pixel, while FIG. 6illustrates a top view of adjacent two pixels. FIG. 5 shows across-sectional view cut along A-A′ in FIG. 6, and the same component isdesignated with the same reference numeral in both of these figures. Inaddition, the two pixels illustrated in FIG. 6 are symmetric to eachother with respect to the current supply line 525, and therefore, havethe same structure as each other.

[0065] In FIG. 5, reference numeral 501 denotes a substrate transparentto visible light, and 502 denotes an insulating film containing silicon.As the substrate 501 that is transparent to visible light, a glasssubstrate, a quartz substrate, a crystalline glass substrate, or aplastic substrate (including a plastic film) can be used. As theinsulating film 502 containing silicon, a silicon oxide film, a siliconoxynitride film, or a silicon nitride film can be used.

[0066] In the present specification, TFTs are formed on an insulatingsurface. As the insulating surface, an insulating film (typically aninsulating film containing silicon) or a substrate made of an insulatingbody (typically a quartz substrate) may be used. Accordingly, theexpression “on the insulating surface” means “on the insulating film” or“on the substrate made of the insulating material”.

[0067] On the insulating film 502 containing silicon, a switching TFT601 and a current-controlling TFT 602 are formed with p-channel TFTs.

[0068] The switching TFT 601 employs, as an active layer, asemiconductor region that includes regions 503 to 505 made of p-typesemiconductor (hereinafter referred to as the p-type semiconductorregions) and regions 506 and 507 made of intrinsic or substantiallyintrinsic semiconductor (hereinafter referred to as the channelformation regions). On the other hand, the current-controlling TFT 602employs, as an active layer, a semiconductor region including p-typesemiconductor regions 508 and 509 and a channel formation region 510.

[0069] The p-type semiconductor region 503 or 505 serves as a sourceregion or a drain region of the switching TFT 601. Furthermore, thep-type semiconductor region 508 serves as a source region of thecurrent-controlling TFT 602, while the p-type semiconductor region 509serves as a drain region of the current-controlling TFT 602.

[0070] The active layers of the switching TFT 601 and thecurrent-controlling TFT 602 are covered with a gate insulating film 511,and further thereon, a source wiring 512, a gate electrode 513 a, a gateelectrode 513 b, a drain wiring 514, and a gate electrode 515 areformed. These components are simultaneously formed with the identicalmaterial. As the constituent material for these lines or electrodes,tantalum, tungsten, molybdenum, niobium, titanium, or a nitride of thesemetals may be used. Alternatively, an alloy in which these metals arecombined, or a silicide of these metals, may be used.

[0071] Furthermore, as shown in FIG. 6, the drain wiring 514 isintegrated with the gate electrode 515. In addition, the gate electrodes513 a and 513 b are integrated with the shared gate wiring 516, so thatthe same voltage is always being applied to these gate electrodes 513 aand 513 b.

[0072] Moreover, in FIG. 5, reference numeral 517 denotes a passivationfilm made of a silicon oxynitride film or a silicon nitride film, and aninterlayer insulating film 518 is formed thereon. As the interlayerinsulating film 518, an insulating film containing silicon or an organicresin film is used. As the organic resin film, a polyimide film, apolyamide film, an acrylic resin film, or a BCB (benzocyclobutene) filmcan be used.

[0073] Further on the interlayer insulating film 518, connecting wirings519 to 522 and an electrode 523 made of a transparent conductive filmare formed. At the same time, line 524 as shown in FIG. 6 are alsosimultaneously formed. As the transparent conductive film, a thin filmmade of indium oxide, tin oxide, zinc oxide, a compound of indium oxideand tin oxide, a compound of indium oxide and zinc oxide, or a compoundobtainable by adding gallium to these materials can be used.

[0074] In this case, the connecting wiring 520 is a line that provideselectrical connection between the source wiring 512 and the p-typesemiconductor region 503. While the connecting wiring 521 is a line thatprovides electrical connection between the p-type semiconductor region505 and the drain region 514. Moreover, the connecting wiring 522 is aline that provides electrical connection between the source region 508and the current supply line (see FIG. 6) 525.

[0075] The connecting wiring 519 is a line that realizes connectionsamong the gate wirings 516 divided and formed into a plurality ofpatterns, and is provided to overpass the source wiring 512 and thecurrent supply line 525. It is also possible to connect the sourcewiring or the current supply line, divided into a plurality of portions,with the connecting wiring formed so as to overpass the gate wiring.

[0076] An electrode 523 is an anode of the EL element, and is referredto as the pixel electrode or the anode in the present specification. Thepixel electrode 533 is electrically connected to a drain region 509 ofthe current-controlling TFT 602. In FIG. 6, the pixel electrode 523 canbe considered as a drain wiring of the current-controlling TFT 602.

[0077]FIG. 7(A) shows a cross-sectional view obtainable by cutting FIG.6 along B-B′. As shown in FIG. 7(A), the connecting wiring 524overpasses the current supply line 525 and provides connection among thegate wirings 516. In addition, FIG. 7(B) shows a cross-sectional viewobtainable by cutting FIG. 6 along C-C′. As shown in FIG. 7(B), theconnecting wiring 522 electrically connects the p-type semiconductorregion 508 of the current-controlling TFT 602 with the current supplyline 525.

[0078] In the actual device, an EL layer (not shown) and a cathode (notshown) are formed thereafter on the pixel electrode 523 to complete anactive-matrix type light-emitting device. The EL layer and the cathodemay be formed with any known technique.

[0079] Furthermore, although a TFT having a top-gate structure(specifically, a planar-type TFT) has been described as an example inthe above, the present invention is not limited to such a kind of TFTstructure. Alternatively, the present invention can be applied to a TFThaving a bottom-gate structure. Typically, it is possible to embody thepresent invention in a reverse-staggered type TFT.

[0080] With the pixel structure as described in the above, thefabrication process for the active-matrix type light-emitting device canbe significantly simplified, and an inexpensive active-matrix typelight-emitting device can be produced. In addition, an electricalapparatus that employs the same as a display section can be realized.

Embodiment 2

[0081] In the present embodiment, the fabrication process of anactive-matrix type light-emitting device in which a pixel section and adriver circuit for transmitting a signal to the pixel section are formedon the identical insulating surface will be described with reference toFIGS. 8(A) to 8(D) and FIGS. 9(A) to 9(C).

[0082] First, as shown in FIG. 8(A), an underlying film (insulatingbody) 802 is formed on a glass substrate 801. In the present embodiment,the underlying film 802 is formed by sequentially depositing a firstsilicon oxynitride film having a thickness of 50 nm and a second siliconoxynitride film having a thickness of 200 nm in this order from the sidecloser to the glass substrate 801. The nitrogen content of the firstsilicon oxynitride film is larger than that of the second siliconoxynitride film so as to suppress diffusion of alkali metal from theglass substrate 801.

[0083] Then, an amorphous silicon film (not shown) is formed on theunderlying film 802 by a plasma CVD method to have a thickness of 40 nm.Thereafter, the amorphous silicon film is irradiated with laser lightfor crystallization to form a polycrystalline silicon film (polysiliconfilm) 803. It should be noted that a microcrystalline silicon film or anamorphous silicon germanium film may be formed instead of the amorphoussilicon film. Moreover, a method for crystallization is not limited tothe laser crystallization method, but any other known crystallizationmethod can be used.

[0084] Then, as shown in FIG. 8(B), the polycrystalline silicon film 803is patterned to form respective independently isolated semiconductorlayers 804 to 806. Upon completion, the semiconductor layer denoted withreference numeral 804 becomes an active layer of a TFT that forms adriver circuit (this TFT is referred to as driver TFT). On the otherhand, the semiconductor layer denoted with reference numeral 805 becomesan active layer of the switching TFT, while that denoted with referencenumeral 806 denotes an active layer of the current-controlling TFT.

[0085] Thereafter, a gate insulating film 807 with a thickness of 80 nm,made of a silicon oxide film, is formed by a plasma CVD method so as tocover the isolated semiconductor layers 804 to 806. Furthermore, atungsten film (not shown) is formed by a sputtering method on the gateinsulating film 807 to have a thickness of 350 nm, and is then patternedto form gate electrodes 808, 809, 810 a, and 810 b. Simultaneously, asource wiring 812 and a drain wiring 813 of the switching TFT areformed. Of course, the drain wiring 813 and the gate electrode 811 areformed integrally.

[0086] Then, elements belonging to Group 13 in the periodic table areadded with the gate electrodes 808, 809, 810 a, 810 b, the source wiring812 and the drain wiring 813 being used as a mask. Any known methods maybe used for the above purpose. In the present embodiment, boron is addedby a plasma doping method at the concentration in the range of 5×10¹⁹ to1×10²¹ atoms/cm³. Thus, the semiconductor regions with the p-typeconductivity (hereinafter referred to as the p-type semiconductorregions) 814 to 821 are formed. Furthermore, channel formation regions822 to 826 are formed immediately below the gate electrodes 808, 809,810 a, and 810 b.

[0087] It should be noted that in the present embodiment, the p-typesemiconductor regions 814 and 816 serve as source regions of thep-channel TFTs forming the driver circuit, while the p-typesemiconductor region 815 serves as a drain region of the p-channel TFTforming the driver circuit.

[0088] Thereafter, a heat treatment is performed to activate theelements in the Group 13 of the periodic table contained in the p-typesemiconductor regions. This activation process may be performed byeither one of a furnace annealing method, a laser annealing method, anda lamp annealing method, or any combination thereof. In the presentembodiment, a heat treatment is performed at 500° C. for four (4) hoursin nitrogen atmosphere. In this case, it is preferable to reduce theconcentration of oxygen in the nitrogen atmosphere to as low a level aspossible. The active layers of the TFTs are formed by the aboveactivation process.

[0089] After the activation process is completed, a silicon oxynitridefilm with a thickness of 200 nm is formed as a passivation film 827, anda hydrogenation process for the semiconductor layers is then performed.Any known hydrogen annealing technique or a plasma hydrogenationtechnique may be used for the hydrogenation process. Thus, the structureas shown in FIG. 8(C) can be obtained.

[0090] Thereafter, as shown in FIG. 8(D), an interlayer insulating film828 made of a resin is formed to have a thickness of 800 nm. As theresin for this purpose, polyimide, polyamide, acrylic resin, epoxyresin, or BCB (benzocyclobutene) may be used. Alternatively, aninorganic insulating film may be also used.

[0091] Contact holes are then formed in the interlayer insulating film828, and connecting wirings 829 to 835 and a pixel electrode 836 areformed. In the present embodiment, a conductive film made of a compoundof indium oxide and tin oxide (Indium Tin Oxide; ITO) is used forforming the connecting wirings 829 to 835 and the pixel electrode 836.It should be noted that of course, any conductive films made of othermaterials that are transparent to visible light can be used for thispurpose.

[0092] The connecting wirings 829 and 831 serve as source wirings of thep-channel TFTs forming the driver circuit, while the connecting wiring830 serves as a drain wiring of the p-channel TFT forming the drivercircuit. Thus, in the present embodiment, the driver circuit is formedbased on a PMOS circuit which is formed of p-channel TFTs.

[0093] In the above-described state, the p-channel TFTs forming thedriver circuit as well as the switching TFT and the current-controllingTFT in the pixel section are completed. In the present embodiment, allof the TFTs are of the p-channel type. It should be noted that theswitching TFT is formed such that the gate electrode thereof overpassesthe active layer at two different positions so that the two channelformation regions are connected to each other in series. Such astructure can effectively suppress an OFF current value (i.e., a currentthat flows when a TFT is in the OFF state).

[0094] Then, as shown in FIG. 9(A), insulating bodies 837 and 838 madeof a resin are formed so as to cover edge portions and concave portions(recesses formed due to the contact holes) of the pixel electrode 836.These insulating bodies 837 and 838 may be formed by forming aninsulating film made of a resin and then patterning the film. In thiscase, it is desirable to set a height (d) from the surface of the pixelelectrode 836 to the top of the insulating body 838 to be at 300 nm orless (preferably 200 nm or less). It should be noted that the insulatingbodies 837 and 838 may be omitted.

[0095] The insulating body 837 is formed for the purpose of covering theedge portions of the pixel electrode 836 and thereby avoiding an adverseeffect of electric field concentration at the edge portions. Thus,deterioration of the EL layer can be prevented. On the other hand, theinsulating body 838 is formed for the purpose of burying the concaveportions of the pixel electrode which are formed due to the contactholes. Thus, any coverage defect of the EL layer to be later formed canbe prevented, and any short-circuit between the pixel electrode and acathode to be later formed can be prevented.

[0096] Thereafter, an EL layer 839 with a thickness of 70 nm and acathode 840 with a thickness of 300 nm are formed by a vapor depositionmethod. In the structure of the present embodiment, a copperphthalocyanine layer (hole injection layer) with a thickness of 20 nmand an Alq₃ layer (light-emitting layer) with a thickness of 50 nm areformed as the EL layer 839. It should be noted that any other knownstructure in which a hole injection layer, a hole transport layer, anelectron transport layer or an electron injection layer are combined maybe used for the light-emitting layer.

[0097] In the present embodiment, the copper phthalocyanine layer isfirst formed to cover all of the pixel electrodes, and thereafter, ared-color light-emitting layer, a green-color light-emitting layer, or ablue-color light-emitting layer are formed for each of the pixelscorresponding to red, green and blue colors, respectively. The regionsto which the layer is to be formed may be selected upon vapor depositionby means of a shadow mask. Thus, a color display can be realized.

[0098] When the green-color light-emitting layer is to be formed,Alq(tris-8-quinolinolato aluminum complex) is used as a mother materialof the light-emitting layer, and quinacridon or coumarine 6 is used as adopant. When the red-color light-emitting layer is to be formed, Alq₃ isused as a mother material of the light-emitting layer, and DCJT, DCM1,or DCM2 is used as a dopant. When the blue-color light-emitting layer isto be formed, BAlq₃ (a complex with five coordinations having a mixedligand of 2-methyl-8-quinolinol and phenol derivative) is used as amother material of the light-emitting layer, and perylene is used as adopant.

[0099] It should be noted that the present invention is not limited touse of the above-mentioned organic materials, but rather, any knownlow-molecule type organic EL material, high-molecule type organic ELmaterial, or inorganic EL material can be used. Alternatively, anycombination of these materials can be also used. Furthermore, in thecase where a high-molecule type organic EL material is used, a coatingmethod can be used.

[0100] In the manner as mentioned in the above, the EL element composedof pixel electrode (anode) 836, EL layer 839 and cathode 840 is formed(see FIG. 9(B)).

[0101] Thereafter, a cover member 842 is bonded by means of an adhesive841. In the present embodiment, a glass substrate is used as the covermember 842. Alternatively a flexible plastic film, a quartz substrate, aplastic substrate, a metal substrate, a silicon substrate, or a ceramicsubstrate may be used. It is advantageous to provide an insulating filmcontaining silicon or a carbon film on a surface exposed to thesurrounding air so as to prevent oxygen or water from entering or toprovide protection against scratches caused by friction.

[0102] As the adhesive 841, a UV curable resin or a thermosetting resinis typically used. For example, PVC (polyvinyl chloride), acrylic resin,polyimide, epoxy resin. silicone resin, PVB (polyvinyl butyral), or EVA(ethylene vinyl acetate) can be used. In the case where the adhesive 841is positioned in the side closer to an observer when viewed from the ELelement, the adhesive is required to be made of a material that allowslight to pass therethrough. In addition, it is advantageous to provide awater-absorbing material (preferably barium oxide) and/or ananti-oxidization material (i.e., a substance that adsorbs oxygen) withinthe adhesive 841 for preventing deterioration of the EL element.

[0103] With the above-described structure, the EL element can becompletely shut out from the ambient air. Thus, deterioration of the ELmaterial due to oxidation can be substantially completely suppressed, sothat reliability of the resultant EL element can be significantlyimproved.

[0104] The active-matrix type light-emitting device thus fabricated inthe above-described manner has the pixel section that includes thecircuit structure as shown in FIG. 10. Specifically, in FIG. 10,reference numeral 1001 denotes a source wiring, 1002 denotes a gatewiring, 1003 denotes a switching TFT, 1004 denotes a current-controllingTFT, 1005 denotes a current supply line, and 1006 denotes an EL element.In the present embodiment, each of the switching TFT 1003 and thecurrent-controlling TFT 1004 is formed as the p-channel TFT.

[0105] It should be noted that a gate capacitance of thecurrent-controlling TFT 1004 exhibits the same function as the capacitoremployed in the conventional art (i.e., the capacitor 404 in FIG. 4).This can be realized because in the case where a time-divisionalgrayscale display is performed by means of a digital driving scheme,necessary charges can be retained only by the gate capacitance of thecurrent-controlling TFT since one-frame period (or one-field period) isshort.

[0106] The active-matrix type light-emitting device of the presentinvention as described in the above requires only five masks in totalfor performing the patterning steps (this number can be further reducedto four when the insulating bodies 837 and 838 are omitted), which canin turn realize a high fabrication yield and a low fabrication cost.

Embodiment 3

[0107] In Embodiment 2 mentioned in the above, the circuit structure ofthe pixel section shown in FIG. 10 can be modified as shown in FIG. 11.Specifically, in FIG. 11, reference numeral 1101 denotes a sourcewiring, 1102 denotes a gate wiring, 1103 denotes a switching TFT, 1104denotes a current-controlling TFT, 1105 denotes a current supply line,and 1106 denotes an EL element. In the present embodiment, each of theswitching TFT 1103 and the current-controlling TFT 1104 is formed as thep-channel TFT. In this case, since the gate wiring 1102 and the currentsupply line 1105 are disposed in different layers, it is advantageous toprovide these components so as to overlap each other with an interlayerinsulating film interposed therebetween. Thus, an occupied area of theselines can be substantially made common, and therefore, the effectivelight-emission area of the pixel can be increased.

Embodiment 4

[0108] In the present embodiment, the active-matrix type light-emittingdevice is fabricated in the manner different from that described inEmbodiment 1. The fabrication process will be described below withreference to FIGS. 12(A) to 12(C).

[0109] First, the fabrication steps up to the one as shown in FIG. 8(D)are performed as described previously in connection with Embodiment 2 toform connecting wirings 1201 to 1207 and a drain wiring 1208. In thepresent embodiment, these connecting wirings are formed of a metal film.Although any material can be used as the metal film, a layered filmhaving a three-layer structure in which an aluminum film is sandwichedbetween titanium films is employed in the present embodiment.

[0110] Then, as shown in FIG. 12(B), a pixel electrode 1209 made of atransparent conductive film is formed. In this case, the pixel electrode1209 is formed such that a portion thereof comes into contact with thedrain wiring 1208. The current-controlling TFT and the pixel electrodecan be thus electrically connected to each other. FIG. 13 shows a topview in the above-described structure. It should be noted that thecross-sectional view shown in FIG. 12(B) is obtainable by cutting FIG.13 along A-A′.

[0111] In the present embodiment, the connecting wirings 1201 to 1207can be made of a metal film. Accordingly, as compared to the transparentconducting film such as an ITO film or the like described in theprevious embodiment modes, a reduction in a wiring resistance as well asa reduction in a contact resistance can be realized. Moreover, all ofthe lines for connecting various circuit portions in the driver circuitcan be made of a low-resistance metal film, and therefore, a drivercircuit capable of exhibiting a higher operating speed can be realized.

[0112] Although the pixel electrode 1209 is formed after the connectingwirings 1201 to 1207 and the drain wiring 1208 are completed, thisfabrication order may be reversed. In other word, the connecting wiringsand the drain wiring made of a metal film may be formed after the pixelelectrode made of a transparent conductive film is formed.

[0113] Thereafter, as in Embodiment 2, an insulating body 1210 made of aresin is formed, and an EL layer 1211 and a cathode 1212 aresequentially formed. Furthermore, a cover member 1214 is formed with anadhesive 1213. Thus, the active-matrix type light-emitting device asshown in FIG. 12(C) is completed.

Embodiment 5

[0114] In the present embodiment, an example of fabricating theactive-matrix type light-emitting device in accordance with the presentinvention with a plastic substrate or a plastic film will be explained.Plastics that can be used in the present embodiment include PES(polyethylene sulfile), PC (polycarbonate), PET (polyethyleneterephthalate), or PEN (polyethylene naphthalate).

[0115] First, the TFTs and the EL element are formed on the glasssubstrate 801 in accordance with the fabrication steps as described inEmbodiment 2. In the present embodiment, however, a peeling layer 1401is formed between the glass substrate 801 and the underlying film 802. Asemiconductor film can be used as the peeling layer 1401. Typically, anamorphous silicon film may be used for the above purpose.

[0116] Moreover, in the present embodiment, a cover member 1403 isadhered by means of a first adhesive 1402. An insulating film made of aresin (typically polyimide, acrylic resin, polyamide, or epoxy resin) isused as the first adhesive 1402. It should be noted that the materialfor the first adhesive 1402 is required to realize a sufficientselection ratio upon etching of the peeling layer 1401 by means of a gascontaining halogen fluoride. As the cover member 1403 to be adhered withthe first adhesive 1404, a PET film is used in the present embodiment.

[0117] Then, the entire substrate on which the element has been formedis exposed to the gas containing halogen fluoride. This treatment allowsthe peeling layer 1401 to be selectively removed. Halogen fluoriderefers to a substance that can be expressed as the chemical formula ofXFn (where X indicates a halogen other than fluorine, and n is aninteger). For example, as the halogen fluoride, chlorine monofluoride(CIF), chlorine trifluoride (ClF₃), bromine monofluoride (BrF), brominetrifluoride (BrF₃), iodine monofluoride (IF), iodine trifluoride (IF₃)can be used.

[0118] Halogen fluoride exhibits a large selection ratio between asilicon film and a silicon oxide film, thereby resulting in a selectiveetching of the silicon film being realized. Furthermore, this etchingreaction can easily proceed at room temperature, and therefore, theprocess can be performed even after the EL element with lowheat-resistance capability is formed.

[0119] Although the silicon film can be etched only by being exposed tothe above-mentioned halogen fluoride, other fluorides (carbontetrafluoride (CF₄) or nitrogen trifluoride) may be used in the presentinvention so long as they are put into a plasma condition.

[0120] In the present embodiment, chlorine trifluoride (CIF₃) is used ashalogen fluoride and nitrogen is used for a dilution gas. Argon, helium,or neon may be used as the dilution gas. Flow rates of both of the gasesmay be set at 500 sccm (8.35×10⁻⁶ m³/s), and a reaction pressure may beset in the range from 1 to 10 Torr (1.3×10² to 1.3×10³ Pa). Moreover, atreatment temperature may be set at room temperature (typically in therange from 20 to 27° C.).

[0121] Thereafter, as shown in FIG. 14(C), a substrate (bondingsubstrate) 1405 made of a plastic substrate or a plastic resin isadhered by means of a second adhesive 1404. In the present embodiment, aPET film is used as the bonding substrate 1405. It is desirable for thecover member 1403 and the bonding substrate 1405 to be made of the samematerial as each other in order to satisfy a stress balance condition.

[0122] Thus, the active-matrix type light-emitting device in which theTFTs and the EL element are sandwiched by the plastic film can beobtained. Since the plastic film is bonded after the TFTs are formed inthe present embodiment, no limitation is applied onto the fabricationprocess. For example, the TFTs can be formed without taking theheat-resistance capability of the plastic to be employed intoconsideration.

[0123] Furthermore, since a flexible, light-weighted light-emittingdevice can be obtained, the device in the present embodiment is suitableto a display section of portable information equipment such as a mobilephone, an electronic databook or the like.

[0124] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 4.

Embodiment 6

[0125] In the present invention, it is advantageous to provide a DLC(diamond-like carbon) film on one side or both sides of the substrate orthe cover member on which the TFTs and the EL element are to be formed.It should be noted that a thickness of such a DLC film is desirably notgreater than 50 nm (more preferably in the range of 10 to 20 nm) sincetoo large a thickness thereof causes transmittance of the film to bereduced. In addition, the DLC film may be formed by a sputtering methodor an ECR plasma CVD method.

[0126] The DLC film is characterized by the Raman spectrum distributionincluding an asymmetric peak at around 1550 cm⁻¹, and a shoulder ataround 1300 cm⁻¹. Moreover, the DLC film is also characterized by thehardness in the range of 15 to 25 Pa when measured by means of amicro-hardness tester. Furthermore, it is advantageous to provide theDLC film as a protection film for surface protection and/or heatdissipation since the DLC film has a larger hardness and a larger heatconductivity as compared to the substrate or the cover member.

[0127] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 5.

Embodiment 7

[0128] In the present embodiment, external appearance views of thelight-emitting device of the present invention as described inEmbodiment 2 will be described. FIG. 15(A) shows a top view of thelight-emitting device of the present invention, while FIG. 15(B) shows across-sectional view thereof.

[0129] In FIG. 15(A), reference numeral 1501 denotes a substrate, 1502denotes a pixel section, 1503 denotes a source-side driver circuit, and1504 denotes a gate-side driver circuit. Each of these driver circuitsis connected via a wiring 1505 to an FPC (flexible printed circuit)1506, which in turn is connected to an external apparatus. The gate-sidedriver circuit shown in FIG. 1 is used in the gate-side driver circuit1504 in FIG. 15(A), while the source-side driver circuit shown in FIG. 3is used in the source-side driver circuit 1503 in FIG. 15(A).Furthermore, the pixel section shown in FIG. 5 is used in the pixelsection 1502 in FIG. 15(A). In this case, a first sealing member 1511, acover member 1512, an adhesive 1513 (see FIG. 15(B)), and a secondsealing member 1514 are formed so as to surround the pixel section 1502,the source-side driver circuit 1503, and the gate-side driver circuit1504.

[0130]FIG. 15(B) corresponds to the cross-sectional view obtainable bycutting FIG. 15(A) along A-A′. In this case, a region surrounded with adashed line 1500 corresponds to the cross-sectional view shown in FIG.9(C), and accordingly, any detailed descriptions thereof will be omittedhere.

[0131] A cathode of the EL element is electrically connected to thewiring 1505 in the region denoted by reference numeral 1514. The wiring1505 is provided to supply a predetermined voltage to the cathode, andis electrically connected to the FPC 1506 via an anisotropic conductivefilm 1515. Furthermore, the EL element is surrounded with the firstsealing member 1511 and the cover member 1512 which is bonded to thesubstrate 1501 by the first sealing member 1511. The EL element isencapsulated with an adhesive 1513.

[0132] Furthermore, a spacer may be contained in the adhesive 1513. Inthis case, if the spacer is formed of barium oxide, it is possible toallow the spacer itself to have water-absorbing capability. In the casewhere the spacer is provided, it is advantageous to provide on acathode, a resin film as a buffer layer for mitigating a pressure fromthe spacer.

[0133] The wiring 1505 is electrically connected to the FPC 1506 via theanisotropic conductive film 1515. The wiring 1505 transmits to the FPC1506 the signal to be sent to the pixel section 1502, the source-sidedriver circuit 1503, and the gate-side driver circuit 1504. The wiring1505 is electrically connected to the external apparatus by the FPC1506.

[0134] Furthermore, in the present embodiment, the second sealing member1514 is provided to cover an exposed portion of the first sealing member1511 and a portion of the FPC 1506, so that the EL element can becompletely shut out from the ambient air. The light-emitting devicehaving the cross-sectional structure shown in FIG. 15(B) is thusobtained. The light-emitting device in the present embodiment can befreely combined with any structures in Embodiments 1 through 6.

Embodiment 8

[0135] In the present embodiment, the pixel structure of thelight-emitting device in accordance with the present invention will bedescribed with reference to FIGS. 16(A) and 16(B). In the presentembodiment, reference numeral 1601 denotes a source wiring of aswitching TFT 1602, 1603 denotes a gate wiring of the switching TFT1602, 1604 denotes a current-controlling TFT, 1605 denotes a capacitor(that can be omitted), 1606 denotes a current supply line, 1607 denotesa power source controlling TFT, 1608 denotes an EL element, and 1609denotes a power source controlling line. In this case, the source wiring1601, the gate wiring 1603, the current supply line 1606, and the powersource controlling line 1608 are formed of the identical conductive filmin the same layer.

[0136] With respect to operations of the power source controlling TFT1607, reference can be made to Japanese Patent Application No.11-341272. It should be noted that in the present embodiment, the powersource controlling TFT is formed as the p-channel type that has thestructure identical to that of the current-controlling TFT.

[0137] Although the power source controlling TFT 1607 is providedbetween the current-controlling TFT 1604 and the EL element 1608 in thepresent embodiment, it is also possible to provide thecurrent-controlling TFT 1604 between the power source controlling TFT1607 and the EL element 1608. Furthermore, the power source controllingTFT 1607 is preferably formed to have the identical structure with thecurrent-controlling TFT 1604, or to be connected in series with thecurrent-controlling TFT 1604 while utilizing the identical active layerthereto.

[0138]FIG. 16(A) illustrates an example in which the current supply line1606 is shared with the two pixels. More specifically, the two pixelsare formed to be symmetric to each other with respect to the currentsupply line 1606. In this case, the number of the necessary currentsupply lines can be reduced, and thus the pixel section can be formedwith higher precision. On the other hand, FIG. 16(B) illustrates anexample in which the current supply line 1610 is arranged in parallel tothe gate wiring 1603, while the current controlling line 1611 isarranged in parallel to the source wiring 1601.

[0139] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 7.

Embodiment 9

[0140] In the present embodiment, the pixel structure of thelight-emitting device in accordance with the present invention will bedescribed with reference to FIGS. 17(A) and 17(B). In the presentembodiment, reference numeral 1701 denotes a source wiring of aswitching TFT 1702, 1703 denotes a gate wiring of the switching TFT1702, 1704 denotes a current-controlling TFT, 1705 denotes a capacitor(that can be omitted), 1706 denotes a current supply line, 1707 denotesan erasing TFT, 1708 denotes an erasing gate wiring, and 1709 denotes anEL element. In this case, the source wiring 1701, the gate wiring 1703,the current supply line 1706, and the erasing gate wiring 17()8 areformed of the identical conductive film in the same layer.

[0141] With respect to operations of the erasing TFT 1707, reference canbe made to Japanese Patent Application No. 11-338786. It should be notedthat in the present embodiment, the power source controlling TFT isformed as the p-channel type that has the structure identical to that ofthe current-controlling TFT. In the above-mentioned Japanese PatentApplication No. 11-338786, the erasing gate wiring is referred to as theerasing gate signal line.

[0142] A drain of the erasing TFT 1707 is connected to a gate of thecurrent-controlling TFT 1704, SO that a gate voltage of thecurrent-controlling TFT 1704 can be forceably changed. It is preferableto form the erasing TFT 1707 as a p-channel TFT that has the samestructure as the switching TFT 1702 so that an OFF current can bereduced.

[0143]FIG. 17(A) illustrates an example in which the current supply line1706 is shared between the two pixels. Namely, the two pixels are formedto be symmetric to each other with respect to the current supply line1706. In this case, the number of the necessary current supply lines canbe reduced, and thus the pixel section can be formed with higherprecision. On the other hand, FIG. 17(B) illustrates an example in whichthe current supply line 1710 is arranged in parallel to the gate wiring1703, while the erasing gate wiring 1711 is arranged in parallel to thesource wiring 1701.

[0144] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 7.

Embodiment 10

[0145] The light-emitting device in accordance with the presentinvention may have a structure in which several TFTs are provided in onepixel. Although Embodiments 8 and 9 have described examples in which thethree TFTs are provided in one pixel, four through six TFTs may beprovided. The present invention is not limited to the pixel structure ofthe light-emitting device, but can be embodied in other structures.

[0146] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 7.

Embodiment 11

[0147] In the present embodiment, a film formation apparatus to be usedfor forming the EL layer and the cathode will be described withreference to FIG. 18. Specifically, in FIG. 18, reference numeral 1801denotes a transportation chamber (A) in which a transportation chamber(A) 1802 is provided for realizing transportation of a substrate 1803.The transportation chamber (A) 1801 includes a reduced-pressureatmosphere, and is blocked from other treatment chambers by means ofgates. The substrate is passed from the transportation chamber (A) 1801to the other treatment chambers by means of a transportation mechanism(A) when the corresponding gate is opened.

[0148] A cryopump is used to reduce the pressure in the transportationchamber (A) 1801. An exhaust port 1804 is provided on a side surface ofthe transportation chamber (A) 1801, and the exhaust pump is disposedbelow the exhaust port 1804. Such a structure realizes an advantage inthat a maintenance operation of the exhaust pump can be easilyperformed.

[0149] The respective treatment chambers will be described below. Sincethe transportation chamber (A) 1801 is provided with thereduced-pressure atmosphere, all of the treatment chambers that aredirectly coupled thereto are provided with an exhaust pump (notillustrated). As the exhaust pump, an oil rotary pump, a mechanicalbooster pump, a turbo molecular pump, or a cryopump can be used.

[0150] Reference numeral 1805 denotes a stock chamber in which asubstrate is set (mounted). This chamber is also referred to as aload-lock chamber. The stock chamber 1805 is shielded from thetransportation chamber (A) 1801 by a gate 1800 a, and a carrier (notillustrated) to which the substrate 1803 is set is disposed in thischamber 1805. Furthermore, the stock chamber 1805 is provided with theabove-mentioned exhaust pump as well as a purge line for introducing anitrogen gas or an inert gas with high purity to the stock chamber 1805.

[0151] In the present embodiment, the substrate 1803 is set onto thecarrier with an element formation surface being faced-down. This isintended to facilitate the face-down orientation when films are formedby a vapor deposition method later. In the face-down orientation, filmsare formed on the substrate with the element formation surface of thesubstrate being facing downward. This orientation can suppressattachment of dust on the element formation surface of the substrate.

[0152] Reference numeral 1806 denotes a transportation chamber (B), thatis coupled to the stock chamber 1805 via a gate 1800 b. Thetransportation chamber (B) 1806 is provided with a transportationmechanism (B) 1807. Reference numeral 1808 denotes a baking chamber(bake chamber), that is coupled to the transportation chamber (B) 18()6via a gate 1800 c.

[0153] The baking chamber 1808 is provided with a mechanism forinverting the substrate orientation in the upside-down manner. Namely,the substrate that has been transported in the face-down orientation isonce changed into a face-up orientation in the baking chamber 1808. Thisis intended to allow a treatment in the subsequent spin coater chamber1809 to be performed in the face-up orientation. After the treatment inthe spin coater chamber 1809 is completed, the substrate is returned tothe baking chamber 1808 to be again inverted upside-down into theface-down orientation, and then further returned to the stock chamber1805.

[0154] The spin coater chamber 1809 is coupled to the transportationchamber (B) 1806 via a gate 1800 d. The spin coater chamber 1809 is afilm formation chamber for forming a film containing an EL material byapplying a solution containing the EL material onto the substrate. Inthe spin coater chamber 1809, a high-molecule type (polymer type)organic EL material is mainly formed. In this case, the film formationchamber is always filled with an inert gas such as nitrogen or argon. Inparticular, when a film is formed in the increased-pressure atmosphereat 1 to 5 atoms (preferably 1.5 to 3 atoms), it is possible toeffectively prevent oxygen or water from entering the film formationchamber.

[0155] The EL material to be formed includes, not only that to be usedas a light-emitting layer, but also that to be used as an electroninjection layer or an electron transport layer. Any known high-moleculetype organic EL material can be also used. Typical organic EL materialsfor serving as the light-emitting layer include PPV (polyparaphenylenevinylene) derivative, PVK (polyvinyl carbazole) derivative orpolyfluorene derivative. These materials are also referred to asa-conjugated polymer. Furthermore, as the electron injection layer,PEDOT (polythiophene) or PAni (polyaniline) can be used.

[0156] Reference numeral 1810 denotes a treatment chamber for performinga surface treatment to an anode or a cathode to serve as the pixelelectrode of the EL element (hereinafter, this chamber is referred to asthe pre-treatment chamber). The pre-treatment chamber 1810 is shieldedfrom the transportation chamber (A) 1801 by a gate 1800 e. Thepre-treatment chamber can be modified in various manners based on thefabrication process of the EL element to be conducted. In the presentembodiment, the pre-treatment chamber 1810 is configured to heat thepixel electrode at 100 to 120° C. while irradiating the surface thereofwith UV-light. Such a pre-treatment is effective when the anode surfaceof the EL element is to be processed.

[0157] Reference numeral 1811 denotes a vapor deposition chamber forforming the conductive film or the EL material by a vapor depositionmethod. The vapor deposition chamber 1811 is coupled to thetransportation chamber (A) 1801 via a gate 1800 f. The vapor depositionchamber 1811 can be provided therein with a plurality of vapordeposition sources. In addition, it is also possible to cause the vapordeposition sources to be evaporated by resistive-heating or electronbeams to form the intended film.

[0158] The conductive film to be formed in the vapor deposition chamber1811 is provided as an electrode on the cathode side of the EL element.For this purpose, a metal having a relatively small work function,typically an element belonging to Group 1 or Group 2 in the periodictable (typically, lithium, magnesium, cesium, calcium, potassium,barium, sodium, or beryllium), or a metal having a work function whichis close to those thereof can be deposited. Alternatively, aluminum,copper, or silver can be deposited to form a low-resistance conductivefilm. Furthermore, a conductive film made of a compound of indium oxideand tin oxide, or a conductive film made of a compound of indium oxideand zinc oxide, can be formed by the vapor deposition method as atransparent conductive film.

[0159] In the vapor deposition chamber 1811, any known EL materials (inparticular, low-molecule type organic EL materials) can be formed.Typical examples for the light-emitting layer include Alq₃(tris-8-quinolinolato aluminum complex) or DSA (distyl allylenederivative), while typical examples for the charge injection layerinclude CuPc (copper phthalocyanine), LiF (lithium fluoride), or acacK(potassium acetylacetonate). Furthermore, typical examples for thecharge transport layer include TPD (triphenylamine derivative) or NPD(anthracene derivative).

[0160] In addition, it is also possible to perform co-vapor depositionof the above-mentioned EL material and a fluorescent material(typically, coumarine 6, rubrene, Nile red, DCM, quinacridon, or thelike). As the fluorescent material, any known materials may be used.Moreover, it is also possible to perform co-vapor deposition of the ELmaterial and an element belonging to Group 1 or Group 2 in the periodictable, so that a portion of the light-emitting layer can exhibit afunction as the charge transport layer or the charge injection layer.The term co-vapor deposition refers to a vapor deposition method inwhich a plurality of vapor deposition sources are simultaneously heatedto mix different materials with each other during the film formationstage.

[0161] In either case, the vapor deposition chamber 1811 is shieldedfrom the transportation chamber (A) 1801 by means of the gate 1800 f,and the film formation of the EL material or the conductive film can beperformed in vacuum. The film formation is performed with the face-downorientation.

[0162] Reference numeral 1812 denotes an encapsulation chamber (alsoreferred to as the sealing chamber or the grove box), that is coupled tothe transportation chamber (A) 1801 via a gate 1800 g. In theencapsulation chamber 1812, a process for finally sealing the EL elementinto a closed space is performed. This process is intended to providethe formed EL element with protection against oxygen or water. For thispurpose, the EL element is mechanically sealed by means of the covermember. Alternatively, it is also possible to seal the EL element bymeans of a thermosetting resin or a UV-curable resin.

[0163] The cover member is adhered to the substrate with the EL elementformed thereon by means of the thermosetting resin or the UV-curableresin. The resin is cured through a heat treatment or a UV irradiationprocess to form a closed space.

[0164] In the film formation apparatus shown in FIG. 18, a mechanism1813 for UV irradiation is provided within the encapsulation chamber1812 (such a mechanism is referred to as the UV irradiation mechanism1813 hereinafter). Thus, the UV curable resin is allowed to be cured byUV light emitted from this UV irradiation mechanism 1813. The innerpressure of the encapsulation chamber 1812 may be reduced by providingan exhaust pump, or increased while purging the inner space with anitrogen gas or an inert gas having high purity.

[0165] A receiving chamber (path box) 1814 is coupled to theencapsulation chamber 1812. The receiving chamber 1814 is provided witha transportation mechanism (C) 1815 for transporting to the receivingchamber 1814 the substrate for which the encapsulation of the EL elementis completed in the encapsulation chamber 1812. The inner pressure ofthe receiving chamber 1814 can be also reduced by providing an exhaustpump. The receiving chamber 1814 is intended to prevent theencapsulation chamber 1812 from being directly exposed to the ambientair, and the substrate is taken out from the receiving chamber 1814.

[0166] As described in the above, the film formation apparatus shown inFIG. 18 allows the EL element to be completely sealed into a closedspace without being exposed to the ambient air, and accordingly,realizes fabrication of a light-emitting device having a highreliability.

Embodiment 12

[0167] The gate-side driving circuit as shown in FIG. 1 and thesource-side driving circuit as shown in FIG. 3 can be applied, not onlyto the light-emitting device, but also to the liquid crystal displaydevice. An external appearance of the liquid crystal display device inaccordance with the present invention is illustrated in FIG. 19(A),while FIG. 19(B) illustrates the cross-sectional structure of its pixelsection.

[0168] In FIG. 19(A), a pixel section 1901, a gate-side driver circuit1902 and a source-side driver circuit 1903 are formed on a substrate1900. In this case, the pixel section as shown in FIG. 5 is used as thepixel section 1901. Moreover, the gate-side driving circuit shown inFIG. 1 is used as the gate-side driver circuit 1902, while thesource-side driving circuit shown in FIG. 3 is used as the source-sidedriver circuit 1903.

[0169] A gate wiring 1904 and a source wiring 1905 extend from thegate-side driver circuit 1902 and the source-side driver circuit 1903,respectively, and a pixel TFT 1906 is formed at the crossing point ofthe gate wiring 1904 and the source wiring 1905. To the pixel TFT 1906,a retaining capacitance 1907 and a liquid crystal element 1908 areconnected in parallel. Furthermore, connecting wirings 1910 and 1911 areformed to extend from an FPC 1909 to input terminals of the drivercircuits. Reference numeral 1912 denotes a counter substrate.

[0170] In the pixel structure as shown in FIG. 19(B), the p-channel TFT1913 forming the driver circuit and the p-channel TFT 1914 serving asthe switching element may be fabricated in accordance with Embodiment 2described previously. It should be noted that reference numeral 1915denotes an orientation film, 1916 denotes a counter substrate, 1917denotes a light shielding film, 1918 denotes a counter electrode, 1919denotes an orientation film, 1920 denotes a sealing member, 1921 denotesa spacer made of a resin, and 1922 denotes liquid crystal. Thesecomponents may be formed by any known method. Furthermore, the structureof the liquid crystal element is not limited to that described in thepresent embodiment.

Embodiment 13

[0171] Although the examples in which the pixel section and the drivercircuit are formed of p-channel TFTs have been described in Embodiments1 through 10 and 12, it is also possible to form the pixel section andthe driver, only of n-channel TFTs. In this case, the driver circuitsare required to be slightly modified such that, for example, thepolarities of the power source lines are inverted in the drivercircuits.

[0172] In such a case, the anode and the cathode are replaced with eachother, so that the structure of the EL element is reversed. In otherwords, it is preferable to realize a structure in which the cathode isconnected to a drain of the current-controlling TFT. It should be notedthat in Embodiments 8 to 10, all TFTs other than the switching TFT andthe current-controlling TFT, if they exist in the pixel, are formed asthe n-channel TFT.

Embodiment 14

[0173] In the light-emitting device as described in Embodiment 1, it ispreferable to provide a silicon nitride film or a silicon oxynitridefilm as the underlying film 502, and to cover the switching TFT 601 andthe current-controlling TFT 602 with the passivation film 517 includinga silicon nitride film or a silicon oxynitride film.

[0174] In such a structure, the switching TFT 601 and thecurrent-controlling TFT 602 are sandwiched between the silicon nitridefilm or the silicon oxynitride film. Thus, water or movable ions can beeffectively prevented from entering into the device from the externalatmosphere.

[0175] Moreover, it is preferable to provide a silicon nitride film or aDLC (diamond-like carbon) film between the pixel electrode 523 and aplanarization film 518 made of an organic resin formed on thepassivation film 517, and further provide the aforementioned siliconnitride film or DLC film on the cathode.

[0176] In such a structure, the EL element is sandwiched between thesilicon nitride films or the DLC films. Thus, not only water or movableions from the external atmosphere but also oxygen can be effectivelyprevented from entering into the device. Although the organic materialsto be used in the light-emitting layer or the like in the EL element areotherwise likely to be easily oxidized thereby resulting indeterioration, the structure in the present embodiment can allow thereliability of the device to be significantly improved.

[0177] As described in the above, reliability of the entirelight-emitting device can be improved by providing a measure forprotecting the TFTs as well as a measure for protecting the EL element.

[0178] The structure as described in the present embodiment can befreely combined with any structures in Embodiments 1 through 10.

Embodiment 15

[0179] The display device formed by implementing the present inventioncan be used as a display portion of various kinds of electricequipments. For instance, when appreciating a television broadcast orthe like, a display incorporating a 20 to 60 inch diagonal displaydevice of the present invention in a casing may be used. Note that apersonal computer display, a television broadcast receiving display, anda display for exhibiting all information such as a display fordisplaying announcements are included in the displays having the displaydevice incorporated in a casing.

[0180] The following can be given as other electronic equipments of thepresent invention: a video camera; a digital camera; a goggle typedisplay (head mounted display); a navigation system; an audio playbackdevice (such as a car audio stereo or an audio component stereo); anotebook type personal computer; a game apparatus; a portableinformation terminal (such as a mobile computer, a portable telephone, aportable game machine, or an electronic book); and an image playbackdevice equipped with a recording medium (specifically, device providedwith a display portion which plays back images in a recording medium anddisplays the images). Specific examples of these electronic equipmentsare shown in FIGS. 20 and 21.

[0181]FIG. 20A shows a display having a display device incorporated in acasing, and the display contains a casing 2001, a support stand 2002, adisplay portion 2003 and the like. The display device of the presentinvention can be used as the display portion 200(3.

[0182]FIG. 20B shows a video camera, and contains a main body 2101, adisplay portion 2102, a sound input portion 2103, operation switches2104, a battery 2105, an image receiving portion 2106 and the like. Thedisplay device of the present invention can be used as the displayportion 2102.

[0183]FIG. 20C is a portion (right side) of a head mounted EL display,and contains a main body 2201, a signal cable 2202, a head fixing band2203, a display portion 2204, an optical system 2205, a light-emittingdevice 2206 and the like. The present invention can be applied to theself-emitting device 2206.

[0184]FIG. 20D is an image playback device equipped with a recordingmedium (specifically, a DVD playback device), and contains a main body2301, a recording medium (such as a DVD) 2302, operation switches 2303,a display portion (a) 2304, a display portion (b) 2305 and the like. Thedisplay portion (a) 2304 is mainly used for displaying imageinformation. The display portion (b) 2305 is mainly used for displayingcharacter information. The display device of the present invention canbe used as the display portion (a) 2304 and as the display portion (b)2305. Note that the image playback device equipped with the recordingmedium includes devices such as household game machines.

[0185]FIG. 20E shows a portable (mobile) computer, and contains a mainbody 2401, a camera portion 2402, an image receiving portion 2403,operation switches 2404, a display portion 2405 and the like. Thedisplay device of the present invention can be used as the displayportion 2405.

[0186]FIG. 20F is a personal computer, and contains a main body 2501, acasing 2502, a display portion 2503, a keyboard 2504 and the like. Thedisplay device of the present invention can be used as the displayportion 2503.

[0187]FIG. 21A shows a rear type projector (projection TV) comprising amain body 2601, an optical source 2602, a liquid crystal display device2603, a polarization beam splitter 2604, reflectors 2605 and 2606 and ascreen 2607. The present invention is applicable to the liquid crystaldisplay device 2603.

[0188]FIG. 21B shows a front type projector comprising a main body 2701,an optical source 2702, a liquid crystal display device 2703, an opticalsystem 2704 and a screen 2705. The present invention is applicable tothe liquid crystal display device 2703.

[0189] Note that, if the luminance further increases in the future,although not shown, then it will become possible to use thelight-emitting device of the present invention in a front type or a reartype projector by expanding and projecting light containing output imageinformation with a lens, an optical fiber or the like.

[0190] In addition, since the light-emitting device conserves power inthe light-emitting portion, it is preferable to display information soas to make the light-emitting portion as small as possible.Consequently, when using the light-emitting device in a display portionmainly for character information, such as in a portable informationterminal, in particular a portable telephone or an audio playbackdevice, it is preferable to drive the light-emitting device so as toform character information by the light-emitting portions whilenon-light-emitting portions are set as background.

[0191]FIG. 21C shows a portable telephone, and contains a main body2801, a sound output portion 2802, a sound input portion 2803, a displayportion 2804, operation switches 2805, and an antenna 2806. Thelight-emitting device of the present invention can be used as thedisplay portion 2804. Note that by displaying white color characters ina black color background, the display portion 2804 can suppress thepower consumption of the portable telephone. Of course, it is possibleto also use the liquid crystal display device of the present inventionfor the display portion 2804.

[0192]FIG. 21D shows an audio playback device, specifically a car audiostereo, and contains a main body 2901, a display portion 2902, andoperation switches 2903 and 2904. The light-emitting device of thepresent invention can be used as the display portion 2902. Further, acar audio stereo is shown in this embodiment, but a portable type or ahousehold audio playback device may also be used. Note that bydisplaying white color characters in a black color background, thedisplay portion 2904 can suppress the power consumption. This isespecially effective in a portable type audio playback device. Ofcourse, it is possible to also use the liquid crystal display device ofthe present invention for the display portion 2804.

[0193] Thus, the application range of the present invention is extremelywide, whereby it may be employed in electric equipments of all fields.Further, the electric equipments of this embodiment may employ thelight-emitting device having any of the constitutions of Embodiments 1through 14.

[0194] Thus, in accordance with the present invention, the displaydevice can be fabricated with very small number of fabrication steps.Accordingly, a fabrication yield can be increased, while a fabricationcost can be reduced, thereby resulting in an inexpensive display devicebeing fabricated.

[0195] Furthermore, since an inexpensive display device can be provided,various electrical apparatuses which employ the display device in theirdisplay section can be provided at a low price.

What is claimed is:
 1. A display device, comprising: a gate wiring; anda source wiring that is formed on the same surface by the sameconductive film as said gate wiring, wherein said gate wiring overpassessaid source wiring via a connecting wiring, and wherein said connectingwiring is formed on the same surface by the same conductive film as adrain wiring of a current-controlling TFT.
 2. A display device,comprising: a gate wiring; and a source wiring that is formed on thesame surface by the same conductive film as said gate wiring, whereinsaid source wiring overpasses said gate wiring via a connecting wiring,and wherein said connecting wiring is formed on the same surface by thesame conductive film as a drain wiring of a current-controlling TFT. 3.A display device, comprising: a gate wiring; and a source wiring and acurrent supply line that are formed on the same surface by the sameconductive film as said gate wiring, wherein said gate wiring overpassessaid source wiring and said current supply line via a connecting wiring,and wherein said connecting wiring is formed on the same surface by thesame conductive film as a drain wiring of a current-controlling TFT. 4.A display device, comprising: a gate wiring; and a source wiring and acurrent supply line that are formed on the same surface by the sameconductive film as said gate wiring, wherein said source wiringoverpasses said source wiring and said current supply line via aconnecting wiring, and wherein said connecting wiring is formed on thesame surface by the same conductive film as a drain wiring of acurrent-controlling TFT.
 5. A display device, comprising: a pixelsection and a driver circuit that are formed on an insulating surface;wherein said driver circuit comprises a decoder including a plurality ofNAND circuits each formed of a TFT of one conductivity type.
 6. Adisplay device, comprising: a pixel section and a driver circuit thatare formed on an insulating surface; wherein said driver circuitcomprises a decoder including a plurality of NAND circuits each formedof a TFT of one conductivity type, and each of said NAND circuitscomprises n TFTs of said one conductivity type connected to each otherin series and n TFTs of said one conductivity type connected to eachother in parallel.
 7. A display device, comprising: a pixel section anda driver circuit that are formed on an insulating surface; wherein saiddriver circuit comprises a buffer formed of TFTs of one conductivitytype, and said buffer comprising: a first TFT of said one conductivitytype; and a second TFT of said one conductivity type that is connectedto said first TFT in series, and utilizes a drain of said first TFT asits gate.
 8. A display device, comprising: a pixel section and a drivercircuit that are formed on an insulating surface; wherein said drivercircuit comprises: a decoder including a plurality of NAND circuits eachformed of a TFT of one conductivity type; and a buffer formed of TFTs ofsaid one conductivity type, and said buffer comprising: a first TFT ofsaid one conductivity type; and a second TFT of said one conductivitytype that is connected to said first TFT in series and utilizes a drainof said first TFT as its gate.
 9. A display device, comprising: a pixelsection and a driver circuit that are formed on an insulating surface;wherein said driver circuit comprises: a decoder including a pluralityof NAND circuits each formed of a TFT of one conductivity type; and abuffer formed of TFTs of said one conductivity type, each of said NANDcircuits comprises n TFTs of said one conductivity type connected toeach other in series and n TFTs of said one conductivity type connectedto each other in parallel, and said buffer comprising: a first TFT ofsaid one conductivity type; and a second TFT of said one conductivitytype that is connected to said first TFT in series and utilizes a drainof said first TFT as its gate.
 10. A display device according to any oneof claims 5 to 9 , wherein a source wiring and a drain wiring of saidTFT is made of a transparent conductive film.
 11. A display deviceaccording to any one of claims 5 to 9 , wherein said TFT of said oneconductivity type is a p-channel TFT.
 12. A display device according toany one of claims 5 to 9 , wherein said TFT of said one conductivitytype is an n-channel TFT.
 13. A display device according to any one ofclaims 5 to 9 , wherein said pixel section comprises: a gate wiring; anda source wiring that is formed on the same surface by the sameconductive film as said gate wiring, wherein said gate wiring overpassessaid source wiring via a connecting wiring, and said connecting wiringis formed on the same surface by the same conductive film as a drainwiring of a current-controlling TFT.
 14. A display device according toany one of claims 5 to 9 , wherein said pixel section comprises: a gatewiring; and a source wiring that is formed on the same surface by thesame conductive film as said gate wiring, wherein said source wiringoverpasses said gate wiring via a connecting wiring, and said connectingwiring is formed on the same surface by the same conductive film as adrain wiring of a current-controlling TFT.
 15. A display deviceaccording to any one of claims 5 to 9 , wherein said pixel sectioncomprises: a gate wiring; and a source wiring, and a current supply linethat are formed on the same surface by the same conductive film as saidgate wiring, wherein said gate wiring, overpasses said source wiring andsaid current supply line via a connecting wiring, and said connectingwiring is formed on the same surface by the same conductive film as adrain wiring of a current-controlling TFT.
 16. A display deviceaccording to any one of claims 5 to 9 , wherein said pixel sectioncomprises: a gate wiring; and a source wiring and a current supply linethat are formed on the same surface by the same conductive film as saidgate wiring, wherein said source wiring overpasses said gate wiring andsaid current supply line via a connecting wiring, and said connectingwiring is formed on the same surface by the same conductive film as adrain wiring of a current-controlling TFT.
 17. A display deviceaccording to any one of claims 1 to 4 , wherein said connecting wiringis formed in a layer different from said gate wiring and said sourcewiring.
 18. A display device according to any one of claims 1 to 4 ,wherein said connecting wiring is made of a transparent conductive film.19. A display device according to any one of claims 1 to 4 , whereineach of a switching TFT, electrically connected to said source wiring,and said current-controlling TFT are p-channel TFTs.
 20. A displaydevice according to any one of claims 1 to 9 , wherein said displaydevice is a light-emitting device.
 21. A display device according to anyone of claims 1 to 9 , wherein said display device is a liquid crystaldisplay device.
 22. A display device according to any one of claims 1 to9 , wherein said display device is incorporated into an electricequipment selected from said group consisting of a video camera, adigital camera, a goggle type display, a navigation system, an audioplayback device, a notebook type personal computer, a game apparatus, aportable information terminal, and an image playback device equippedwith a recording medium.
 23. A method for fabricating a display device,comprising the steps of: forming a semiconductor layer on an insulatingsurface; forming a gate insulating film on said semiconductor layer;forming a source wiring, a gate wiring and a current supply line on saidgate insulating film; forming a p-type semiconductor region in saidsemiconductor layer; forming an interlayer insulating layer over saidsource wiring, said gate wiring and said current supply line; formingcontact holes respectively reaching said source wiring, said p-typesemiconductor region, and said current supply line; and forming aconnecting wiring providing electrical connection either between saidsource wiring and said p-type semiconductor region or between saidcurrent supply line and said p-type semiconductor region.
 24. A methodfor fabricating a display device, comprising the steps of: forming asemiconductor layer on an insulating surface; forming a gate insulatingfilm on said semiconductor layer; forming a source wiring, a gate wiringand a current supply line on said gate insulating film; forming a p-typesemiconductor region in said semiconductor layer; forming an interlayerinsulating layer over said source wiring, said gate wiring and saidcurrent supply line; forming contact holes respectively reaching saidsource wiring, said p-type semiconductor region, and said current supplyline; and forming a connecting wiring that overpasses said source wiringand connects a plurality of gate wirings to each other.
 25. A method forfabricating a display device according to claim 23 or 24 , wherein saidconnecting wiring is formed on the same surface by the same conductivefilm as a drain wiring of a current-controlling TFT.
 26. A method forfabricating a display device according to any one of claims 23 or 24,wherein said display device is a light-emitting device.
 27. A method forfabricating a display device according to any one of claims 23 or 24,wherein said display device is a liquid crystal display device.
 28. Amethod for fabricating a display device according to any one of claims23 or 24, wherein said display device is incorporated into an electricequipment selected from said group consisting of a video camera, adigital camera, a goggle type display, a navigation system, an audioplayback device, a notebook type personal computer, a game apparatus, aportable information terminal, and an image playback device equippedwith a recording medium.